(Honestly this is a HUUUUUUGE FREEKEN REASON to have more then pre-generated character backgrounds. The fact that anyone who played the game will immediately know what your quest is and can circumvent you with metaknowledge)
So there should be so many elaborate, inter-related quests with conflicting goals, that with prior knowledge of the game (or a wiki/walkthrough) there is no way to anticipate possible conflicts?
You do realize that for competitive questing, every quest line must have competing goals with all other quest lines, right? Not only does that mean each background takes more work than the one before, all background quest lines must become increasingly complex (or at least longer) the more backgrounds there are.
Rather than theory crafting what a game 'should' do assuming unlimited resources, consider that origins are a core component of the game and there are four times the number of writers working on D:OS 2 than D:OS. If there are X origins, how reasonable is it to add on 2 or 3X more, or design adaptable backgrounds that are 5-10 times the work of a specific character?
Also, previous experience with any multiplayer game can always be used to gain an advantage over those who are unfamiliar with it.